Discussion

ClockService object

This ClockService is an example of an object that may come from a library.
And, is injected into the application via an initializer.

During initialization the tick method is called which uses Ember.run.later
with a time of 250 milliseconds as the interval. A property is set at the end
of the interval. Since the tick method observes the incremented property
another interval is triggered each time the property increases.

A controller for a list of comments, each comment will have a new clock
instance when added to the list. The comment item controller sets up
the seconds binding, used by the template to show the time since the
comment was created.

Note

To explore the concept further, try adding a timestamp and updating the clock’s
pulse by comparing the current time. This would be needed to update the pulse
property when a user puts his/her computer to sleep then reopens their browser
after waking.